I didn't post this in Tape because the info the Support engineer got internally indicated that the "cause" (as I perceive it) is an artifact of B & R's database's current referential integrity method.
When beginning the migration to Veeam B & R, I had a repository at an iSCSI LUN, connected in Windows as drive letter "V:\".
Once the old software was done using the local storage ("N:\"), I followed the steps at kb1729 to update the source backup jobs' repositories, removed the old repository, and then removed the drive from Windows.
Backup to Tape jobs run since then continue having an empty reference to the "V:\"-pathed repository.
My questions to, and responses from, the engineer:
- What is the relationship between the source VM and the repository on which its backup is/was stored?".
"During a VM backup to disk, its location (regarding host and datastore) and its reference IDs are stored both in the repository inside the restore point, and it is also stored within our database.
During backup to tape jobs, the tape job will look into the database for records of a latest backup for the VM so that it can be written to tape.
The backup to tape job then writes the catalog to C:\VBRCatalog by default.
The tape catalog has a single reference to a media id within our database which links through a few different tables where we eventually get to a backup id which will hold the information of the repository." - How would Veeam B. & R. use the info about a path to a Repository that it knows doesn’t exist?
Regarding the second question, I after discussion with various colleagues it seems the biggest concern that was voiced the most was that if you were to restore the backups as a file from tape restore and then specified the original location as the destination that it might fail.
However, I did test this myself on one of the tapes that did have a reference to the old repository and it was able to restore to the original location without any problems, so even with the reference still visible it does not seem to pose a threat for future restores.